$\dfrac{1}{12} - \dfrac{6}{8} = {?}$
Answer: $ = {\dfrac{1 \times 2}{12 \times 2}} - {\dfrac{6 \times 3}{8 \times 3}} $ $ = {\dfrac{2}{24}} - {\dfrac{18}{24}} $ $ = \dfrac{{2} - {18}}{24} $ $ = -\dfrac{16}{24}$